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Is it OK to charge my smartphone every night?

Question

Does it affect your iPhone's battery life when you charge it every night? I have found a lot of conflicting answers on the web.

- Madeline

Answer

This question was answered on January 4, 2013.
Much of the information contained herein may have changed since posting.

The mobile revolution is being powered (pun intended!) by sophisticated battery technology, but battery life is still one of the most common complaints from mobile users.

Understanding the nuances of today’s battery technology can help you balance the battery life with convenience for the best overall results.

Most of today’s mobile electronics use Lithium-Ion batteries, which are substantially better than the older Nickel-Cadmium (NiCad) and Nickel metal hydride (NiMH) technology.

Lithium-based batteries are most common because they can store more energy in a smaller package, they don’t dissipate energy as quickly when the device is not being used, they can handle more charge cycles and they are capable of charging up quicker.

Older nickel-based batteries were susceptible to ‘memory’ issues when charging, so the general rule was to always run the battery down to near 0 before recharging.

Lithium-based battery systems don’t have this memory charging issue so this practice is unnecessary for today’s devices (constant full discharges can actually accelerate capacity loss in lithium ion batteries, so keep the full discharges to once a month if possible).

Additionally, for devices that have a ‘gauge’ (such as laptops) it’s a good idea to let the device run all the way down every 30 charges so that the gauge can recalibrate itself.

This will help keep the gauge accurate so it can properly represent the amount of power left.

All batteries have a finite life, which is based on the number of times it’s been recharged (often referred to as charge cycles).

Apples website explains how the charge cycles are calculated:

“A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could listen to your iPod for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle. Each time you complete a charge cycle, it diminishes battery capacity slightly, but you can put notebook, iPod, and iPhone batteries through many charge cycles before they will only hold 80% of original battery capacity.”

You can expect 300-500 charge cycles from lithium-ion batteries before a noticeable decline in battery life occurs (down to 80%) and technically they prefer a partial discharge over a full discharge on a regular basis.

Heat is actually the biggest factor in the life of any battery. The more heat it encounters, the quicker it will degrade.

Leaving your battery-powered devices in a hot car or trunk or in direct sunlight on hot days will do more to kill the life of the battery than anything you do in the charging process.

Never turn on or try to charge a batter y that has been overheated; always allow it to get back to room temperature or you will reduce its life (and do everything you can to avoid the high heat situations entirely).

Although most recharge systems have an auto shutoff to avoid overcharging, as a precaution, try not to leave a fully charged device attached to the charger for extended periods of time (especially if you can feel that the battery is hot).

For convenience sake, go ahead and plug your phone in every night as an incremental change in the overall life of the battery isn’t worth the risk of running out of juice in the middle of the day!